1. Technical Field
The present invention relates to a self-ballasted fluorescent lamp.
2. Background Art
For energy saving, a high efficiency self-ballasted fluorescent lamp that can replace a low efficiency incandescent lamp has been under active development and research in the lighting field.
Conventionally, three types of self-ballasted fluorescent lamps with luminous fluxes equivalent to those of 40 W, 60 W and 100 W of incandescent lamps have been developed. The lamp powers of these types are about 10 W, 14 W and 25 W, respectively, which are about 1/4 of the lamp powers of the incandescent lamps. Thus, the self-ballasted fluorescent lamp can provide a large effect for energy saving. In the early stage of the development, low wattage self-ballasted fluorescent lamps with luminous fluxes equivalent to those of 40 W and 60 W incandescent lamps were subjects for development. Recently, a high wattage fluorescent lamp with a luminous flux of 1520 lm that can replace a 100 W incandescent lamp has been under development. In the development of these fluorescent lamps, in order to promote replacement of a compact incandescent lamp, it is desired to attain a high ratio of the existing light fixtures to which the self-ballasted fluorescent lamp can be applied without modifying the light fixtures (hereinafter, this ratio is referred to as "light fixture application ratio"). For this reason, the development is directed especially to achieving a small lamp shape.
FIGS. 9 and 10 show examples of the shape of a conventional self-ballasted fluorescent lamp. FIG. 9 shows a low wattage fluorescent lamp, and FIG. 10 shows a high wattage fluorescent lamp. The fluorescent lamps include fluorescent tubes 28 and 29, electronic ballast circuit portions 30 and 31, outer bulbs 32 and 33, resin cases 34 and 35, and lamp bases 36 and 37, respectively. When comparing the shape of an incandescent lamp with that of a conventional self-ballasted fluorescent lamp, in an eggplant-shaped incandescent lamp, the outer diameter of the outer bulb is 60 mm and the total length of the lamp is 110 mm, whereas the early-developed low wattage fluorescent lamp has an eggplant-shaped outer bulb 32, which is similar to the incandescent lamp shape, and is fairly compact, where the outer diameter Do of the outer bulb 32 is 60 mm, and the total length Lo of the lamp is 130 mm. Therefore, the light fixture application ratio is as high as about 70%.
On the other hand, it is desired to attain a high light fixture application ratio by producing a further compact high wattage self-ballasted fluorescent lamp (of a conventional lamp power of about 25 W) that can replace the 100 W incandescent lamp, whose replacement is particularly effective for energy saving in the development of the self-ballasted fluorescent lamp replacing the incandescent lamp.
However, regarding the high wattage self-ballasted fluorescent lamp replacing the 100 W incandescent lamp, the outer bulb 33 is cylindrical, as shown in FIG. 10, the outer diameter Do is about 70 mm, and the total length Lo of the lamp is about 150 mm. This is insufficient in terms of compactness, and therefore, the light fixture application ratio is as low as about 40%.
Prior to the development of such a high wattage self-ballasted fluorescent lamp, the inventors of the present invention first examined the shape and the size of various light fixtures for incandescent lamps to specify requirements from the aspect of lamp shape to improve the light fixture application ratio of the lamp. The following requirements are the outcome of this examination.
(i) The outer bulb should have an eggplant shape similar to an incandescent lamp, as shown in FIG. 9, and a narrowed outer diameter at its bottom portion. PA0 (i) The outer diameter Do of the eggplant-shaped outer bulb 32 is 70 mm, the outer diameter Di of the bottom portion is 58 mm, and the total length Li is 85 mm. PA0 (ii) The outer diameter Dc of the resin case is 58 mm. PA0 (iii) The total length Lo of the lamp is 148 mm.
(ii) In addition, the outer diameter of the resin case also should be narrowed.
When these requirements are satisfied, the shoulder of the resin case can be prevented from contacting a reflection plate of the light fixture, which occurred in a conventional high wattage self-ballasted fluorescent lamp, and the light fixture application ratio can be improved. On the other hand, regarding the total length of the lamp, even if it is relatively large, it can be applied to an open type light fixture. However, it is necessary to attain good appearance of the light fixture on which the lamp is mounted. Therefore, it is desired at least to achieve a size not larger than that of the conventional high wattage self-ballasted fluorescent lamp.
It is concluded that when the following requirements are satisfied for the upper limits of the sizes in various portions of the high wattage self-ballasted fluorescent lamp, the light fixture application ratio of the lamp can be raised to about 70%, which is equivalent to that in the case of the low wattage self-ballasted fluorescent lamp.
The lower limit of the lamp size can be defined under the conditions in which predetermined rated values of the characteristics of the lamp including the lifetime can be obtained as described later.
Next, as a preliminary development, the inventors of the present invention measured the characteristics of the lamp including the lifetime with a smaller high wattage self-ballasted fluorescent lamp having the above-described lamp size As a result, it turned out that a first problem in the development of the high wattage self-ballasted fluorescent lamp with a lamp power of about 25 W is that the lifetime of the lamp is short. This is caused primarily by (i) a high level of deterioration of the luminous flux during the lifetime of the lamp due to an excessive increase in the temperature of the fluorescent tube and (ii) occurrence of malfunction of the circuit due to an excessive increase in the temperature of the electronic components of the electronic ballast circuit portion and the PC resin substrate mounted in the narrow resin case.
In particular, the reduction of the lifetime of the lamp due to the factor (ii) is often caused by malfunction of a capacitor component, which terminates the lifetime of the lamp in a relatively short time. In order for a compact high wattage self-ballasted fluorescent lamp replacing the 100 W incandescent lamp to be used widely, it is necessary to ensure 6000 hours or more lifetime, which is equivalent to that of the conventional lamp.
Furthermore, a high efficiency and high wattage self-ballasted fluorescent lamp that consumes power less than about 25 W of the conventional lamp is desired for further energy saving. Desired target values are 23 W or less for the lamp power and 66 lm/W or more for the luminous efficiency of the lamp in order to attain a luminous flux of 1520 lm equivalent to that of the 100 W incandescent lamp.